This project is concerned with studies of the genetic diversity of Trypanosoma cruzi and the implications of this diversity in the presentation and course of Chagas' disease. Major emphasis during the year has centered on four topics: 1) Utilization of the T. cruzi data base and results of multivariant analysis to model and predict the population dynamics of mixtures of clones; 2) Analysis of the patterns of presentation and disease in inbred mice infected with T. cruzi clones; 3) Development of mutant T. cruzi clones for the production of T. cruzi hybrids; 4) Analysis of the inter-relationship between environmental temperature and the respiratory enzymes of T. cruzi clones. The flow cytometer development program is nearing completion. The instrument has been equipped with quartz optics to permit analysis in the deep UV and Coulter volume orifice and electronics. The performance of the Coulter volume system exceeds all previous attempts to incorporate this parameter into a flow cytometer. This has proven to be an important development for the analysis of cells with unusual symmetry such as Giardia lamblia. A MEDLARS-based, computer-processed bibliography of Chagas' disease (1968-1984) has been completed.